1. Field of the Invention
The invention relates to an intermediate dogging device for use in an end dogging log carriage to limit lateral deflection of a log resulting from machining of the log.
2. Prior Art
Log supporting carriages have been used for many years and there are several ways of supporting a log in the carriage. In older conventional carriages, commonly a log is gripped in at least two places spaced from ends of the log to produce overhanging ends. When a relatively large amount of wood is removed from the log, it is not unusual for the ends to move laterally between 3 to 5 mms. In more recently developed end dogging carriages, end faces of the log are engaged by dogs so as to leave side faces of the log free for machining concurrently in a cutting apparatus, such as a pair of spaced bandmills and/or chipper heads. However, end dogging permits unsupported mid portions of the log to move laterally, sometimes to a greater extent than ends of the logs in the older conventional carriages. Deflection of the log is attributed mainly to release of inherent residual stresses within the log by removal of portions of the log, cutting forces applied to the log during machining, and sagging of the log under its own weight. The deflection reduces accuracy of cut and produces vibration problems, and as the diameter of logs being processed is reduced, and accuracy demands for greater log recovery are increased, problems of log deflection become more acute. Also, it can be appreciated that axial end loading of the log to grip the log with the end dogs tends to aggravate lateral deflection of the log in a manner similar to a strut under compression, particularly if the log is curved initially.